Regulatory shift may happen and I think the account my get froze due to those restrictions and worse funds might also got froze if the user will experience bad faith.
No, I don't think so. A regulatory shift doesn't mean immediately freezing your account. If during registration your country wasn't in the restricted list but later they add it. Then they should give you time to withdraw your winnings. This is what every casino should do since they have to follow the regulations, and users have to get back their funds as well.
But they can reach up to the support towards those situation happened since for sure they are aware on those changes and give chance their user to withdraw their funds if there are balance left on their accounts.
Exactly what I stated above. This isn't a chance; this is the users' right, and they have to notify users regarding the issues. Like Exchange, notify users during the delisting of a coin, and even after delisting, users could withdraw their funds.
Also it will be good if they have that automatic notification towards the changes happening so that their players would be aware about the situation happen so they can do some action before they encounter any problems related to that matters on their casino.
They have to send mail to all users who are going to be added to restricted jurisdictions. This isn't really a simple thing to add a country to their restricted zone. The user should know prior to adding to the list.